That's another way of saying the workers inhaled a mist of pig brain tissue and it made them very sick.

Twenty-one of those affected were from Minnesota, while the rest were from Indiana. Many, but not all, of the workers were stationed near a high-powered air compressor used to blow the brains out of pig heads. Researchers say that when workers inhaled the mist, it triggered their immune systems to attack their own nervous systems:

The neurological disorder described is autoimmune in origin and is related to occupational exposure to multiple aerosolised porcine brain tissue antigens. The pattern of nerve involvement suggests vulnerability of nerve roots and terminals where the blood-nerve barrier is most permeable.